icanfixall
Official GMM hand model
Well I still feel you need to know what the block was decked and.. Thats a complete tear down. Also the dimension you posted about the piston deck protrusion height is suspect to be. I have not read how you took those dimensions of 20 outside the cylinder deck. The pistons will rock in the cylinders a small amount. That rocking can really throw off your measurement. The tool I have posted and offered as a loaner is for me the only true way to capture the actual piston height. you zero it. Place it over the cylinder and run the piston up till the dial indicator stops gaining thousands. It takes the measurement off the center or any area you want. As I mentioned. The center of our pistons is where it reads best. Any piston rock will not change the reading if you take it off the center or withing maybe 1/8 to 1/4 inch of dead center. If you find this dimension to be correct at 20 thousands. Well all I can say is the pistons must be milled. I can't tell you what amount needs to me milled off because I can't see what is going on in your engine. But knowing that not ALL the valves contacted the pistons the same tells me something is not correct. Like maybe the heads were decked off square so some valves got closer in the geometry of their action. Measuring the head thickness in several places will tell you if they are true. They can be flat but if the milling was done of an angle from front to back of the head only measuring front and back head thickness will tell what may have been done. You know what cylinder hit hardest. Measure those areas most of all. You will need a 5 to 8 inch mic for this. Factory original head thickness is 4.805 and minimum is 4.795. I still do not understand why the min thickness has anything to do with valve action if all the valves are recessed into the seats like they should be. We run a hydraulic roller lifter and it "makes" its own valve lash usually in the center of the lifter piston riding on the oil cushion.
